Although standby power killers (surge protectors, power strips, UPSs) are available on the market, those devices present numerous drawbacks, and in particular some of them risk damaging appliances connected thereto. There are two main categories of standby power killer, those that operate in master-slave mode and those that are specialized for a given type of application. The second category includes standby power killers for audiovisual equipment that make use of the signals emitted by the remote controls of such equipment, as described for example in Sony's patent JP 2001/268654.
State of the art master-slave standby power killers, e.g. as described in the patent application published under the No. US 2005/0007712 or in U.S. Pat. No. 6,940,272, generally include a relay for switching so-called “slave” loads, with switching being controlled by the current that is consumed by the so-called “master” load that always remains connected to the electricity network. Above the consumption threshold for the master load, which may optionally be adjustable by the user, the relay is closed, and below the threshold the relay opens. A priori, that type of device could serve equally well in a microcomputer environment and in a TV environment, however in practice it is found that state of the art standby power killers do not operate well with certain models of computer and/or TV set. State of the art standby power killers can even turn out to be dangerous for the connected appliances under certain conditions of operation in that they can embark on endless cycles of switching on and switching off that can lead to the destruction of the connected appliances.
In prior art devices, the following drawbacks are generally observed:
the standby power killer is specialized as a function of the type of equipment to which it is to be connected;
the trigger thresholds and the timeout periods depend to some extent on the waveform of the current flowing through the master load;
the accuracy of the switching thresholds and of the timeout period is not sufficient;
hysteresis is insufficient and can lead to ill-controlled switching;
it is not possible to correct for functional anomalies such as infinite loops of switching on and off as can be observed, for example, with certain DVB-T adapters and certain TV sets for which changeovers from the on state to the standby state and vice versa are controlled on the basis of the state of a signal coming from the TV set;
with master-slave models, a master load remains powered continuously, thereby reducing the savings that can be achieved, shortening the lifetime of the appliance, and reducing safety by increasing the risk of fire;
the standby power killer has its own active energy consumption that is not negligible, thereby reducing the saving achieved by using the standby power killer and lengthening the time required for the client to achieve a return on investment; and
standby power killers are found to be fragile in the face of power peaks that might be absorbed by the controlled appliances at the moment they are supplied.
Prior art standby power killers specialized for TV sets and making use of remote control signals by decoding their meaning in order to detect orders to switch on or to switch to standby, present the major drawback of not being compatible with all TV sets. This drawback can be mitigated in part using devices that require prior training with the remote control codes, but it is nevertheless difficult to be compatible with all standards since they also present differences in physical terms, e.g. in terms of the frequency on which the modulation is carried and/or of the infrared wavelength. In addition, that training operation complicates considerably the use of a product that needs to remain simple if it is to be in general use with consumers.
Simplified models of TV standby power killers do no more than detect the presence of a modulated infrared signal and present several drawbacks including numerous false starts by detecting untimely signals that can sometimes involve a sudden change in lighting level being understood as a switch-on signal, in particular when the light sources are of the low consumption type since such sources have the feature of emitting over a broad spectrum.
In addition, the specialization of standby power killers in the state of the art as a function of the type of functional group that is to be connected thereto multiplies the number of different models that need to be manufactured, stored, and sold, which is inefficient, economically speaking.